1. Field of the Invention
The present invention relates to a vehicle braking system.
2. Discussion of the Background
A hybrid vehicle HV that runs by a combination of a driving motor and an internal combustion engine may be provided with a vehicle braking apparatus which includes a hydraulic brake that converts the operation by a brake operating member, such as a brake pedal, into a fluid pressure, such as an oil pressure, and thereby actuates the brake actuating unit and a regenerative brake that causes the driving motor to act as a generator under regenerative control so as to convert the kinetic energy of a moving vehicle into electrical energy and thereby slows down the vehicle or brings it to a stop. Also, engine braking that uses the retarding forces within the internal combustion engine to slow the vehicle down can be used.
Of these brakes, since the regenerative brake can recover the kinetic energy of the hybrid vehicle HV as electrical energy, the energy efficiency of the hybrid vehicle HV can be improved by making an effective use of the braking power by the regenerative brake.
Motor vehicles including the hybrid vehicle described above have been required to shorten a braking distance associated with, in particular, emergency braking, thus various vehicle braking apparatuses have been proposed.
For example, a braking power control apparatus is disclosed in Japanese Patent No. 4089016, which can produce an optimal braking power, irrespective of the different degree of braking power generated by different operations of the brake pedal during emergency braking.
Also, an emergency braking assistance control apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 10-59150, which produces an assistance braking power in an early stage and thereby prevents a delay in braking operation timing.
In addition, a vehicle braking power control apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 10-211833, which forcedly drives a supplementary booster with a vacuum pressure from a negative pressure source during a sudden braking operation and thereby forcedly boosts a brake fluid pressure from a master cylinder so as to apply a harsh braking.
Furthermore, an electric vehicle braking apparatus is disclosed in Japanese Unexamined Patent Application Publication No. 10-229608, which performs friction braking and regenerative braking, depending on the amount of braking operations when it is determined that a braking power assist associated with a harsh braking is necessary.
Also, Japanese Unexamined Patent Application Publications Nos. 10-59150, 10-211833, and 10-229608 disclose a technology for employing an ABS function to suppress skidding on a low-μ road surface.
Furthermore, Japanese Unexamined Patent Application Publication No. 10-229608 discloses a technology for producing a target braking power with a friction braking power and a regenerative braking power and thereby converting the kinetic energy of an electric vehicle into electrical energy.